# cg6_2013 - Computer Graphics Lecture 6 View Transformation...

This preview shows pages 1–21. Sign up to view the full content.

Computer Graphics Lecture ± View Transformation and Clipping Taku Komura

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
&verview • View transformation – Recap of homogeneous transformation – -arallel projection – -erspective projection – ±anonical view volume • ±lipping – 'ine / -olygon clipping
Procedure ±² Transform into camera coordinates² ³done in Lecture ´µ ¶² Perform projection into Y`\Z YROXP\ or VzU\\Q zRRU[`QxW\V± ´² Clip geometry outside the Y`\Z YROXP\ ²

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
View Projection ± Topics ●Homogenous transformation ●Parallel projection ●Perspective projection ●Canonical view volume
±omogeneous Transformations Y.D SURa D Z≖z D z≖O Y O The projection matiix should be ±x± matrices to allow general concatenation

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
±omogeneous ²oordinates
Camera Coordinate System we use ±same as OpenGL² y z x Facing the –z direction X axis facing the right side

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Parallel projections ±Orthographic projection² • Specified by a direction of projection³ rather than a point´ • Objects of same size appear at the same size after the projection
Parallel projection± Orthographic Projection onto a plane at z = ²± x p = x ³ y p = y ³ z = ²±

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Perspective Projection • Objects far away appear smaller± closer objects appear bigger • Specified by a center of projection and the focal distance ²distance from the eye to the projection plane³
Perspective projection d y z Projectio n Plane± P²x³y³ P p ²x p ³y p ³µ Centre of projection at the origin³ Projection plane at z=µd± d¶ focal distance x

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Alternative formulation± z P²x³y³ d x x p z P²x³y³ d y y p Projection plane at z = µ³ Centre of projection at z = d Now we can allow d→∞

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Exercise± where will the two points be projected onto?
Problems • After projection± the depth information is lost • We need to preserve the depth information for hidden surface removal • Objects behind the camera are projected to the front of the camera

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
3± View Volume • The volume in which the visible objects exist – ²or parallel projection, view volume is a box.
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 52

cg6_2013 - Computer Graphics Lecture 6 View Transformation...

This preview shows document pages 1 - 21. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online